Many existing Electronic Warfare (EW) systems have a requirement for a high Radio Frequency (RF) power transmitter (ranging from tens-of-watts to several hundred watts) having performance over a wide instantaneous frequency bandwidth. Currently, these EW systems are completely reliant on the use of Traveling Wave Tube Amplifier (TWTA) technology to achieve the combination of wide frequency bandwidth and high output power performance. Tube based amplifiers, however, may have two very limiting disadvantages: (1) they are relatively large in physical size and (2) they require very high-voltage power supplies (sometimes thousands of volts). These characteristics may limit the use of TWTAs in transmitter applications that cannot support the large size or high-voltage power supply constraints of the tube-based amplifiers.
Transmitter applications may require some form of High Power Amplifier (HPA) to achieve the RF output power specified for a particular transmitter system. Only two approaches are currently available: (1) tube-based amplifier technology or (2) a solid-state solution. The approaches tradeoff output power level for size and reliability. In tube-based solutions, the high power density capability of the TWTA provides superior output power performance. However, the high-voltage power supply requirement for these amplifiers is not suitable for providing a compact form-factor solution. Present wideband solid-state amplifiers, using established gallium arsenide (GaAs) transistor technology, have significantly lower power density and are primarily limited to low to medium RF power applications (usually less than 15 W). Their power density capability requires a significant level of circuit power-combining, which usually limits the obtainable RF output power level.
The GaAs power solid-state amplifiers do, however, offer a smaller size than tube-based approaches. More recently, Microwave Power Modules (MPM) have offered the combination of a solid-state driver amplifier which then feeds a TWTA as the power stage. This combination has offered a smaller form-factor than the tube alone, but a high voltage power supply is still required. In addition, tube-based amplifiers have been associated with reliability concerns and may not be an option in EW systems that cannot accommodate the size and high-voltage power supply constraints of TWTAs. In general, for wideband, high power requirements, the cumbersome TWTA, along with their high-voltage power supply requirements, do not support transmitter systems requiring small form-factors.
Thus, traditional methods of achieving high power transmitters operating over wide bandwidths utilize large form-factor TWTAs. The use of these tube-based approaches does not permit small form-factor amplifier packages due to the large physical size of the tubes and their associated high-voltage power supplies. Therefore, there is a need for systems that provide small, wideband, high power solid-state transmitters.